Edouard Branly Coheres

When CQ published a history of radio titled "Men of Radio" Edouard Branley was one of the three names in Bold beside Hetz and Maxwell.  Today he doesn't get that kind of top billing. If you know nothing else abotu his work at least know about the Branly coherer, which he developed around around 1890.

Branly was a professor of physics at the Catholic institute in Paris.He had not been studying radio but nerves. He had learned they are made of tightly packed fibers and had begun experimenting the properties of fine particles looking for an electrical corollary to what he's observed. His models began with the work of Temistocle Calzecchi-Onesti, who demonstrated in 1885 that iron filings in an glass tube will still conduct an electrical current. (It's also possible he had seen similar work by Alfred Varley)

Calzecchi's experiements ran from 1884 through 1886 and tested a number of metallic particles. The operation of Branly's coherer is largely based upon the electrical resistance offered by loose metal filings. The resistance decreases when current is applied between the terminals of the coherer.  Branly may or may not have been aware but the mechanism relied on the iron oxide on the surface of the filings. Those oxide layers are broken down when a voltage is applied causing the coherer to "latch" into its low-resistance state until the voltage ceases and the coherer is physically "percussed."  We'd probably just call it "tapping." regardless Branley detected resistance changes on the order of 1:1000.

It was actually Sir Oliver Lodge that named it the Coherer. It was a marked improvement on Hertz's spark detector. Branleymay not have been aware that his coherer generated hertzian waves, but Lodge certainly was. Using  Branlys cohoerer. Lodge went wireless signals 100 yards and because of that, Branly won the Nobel prize 30 years later. Branly died in 1940.

Oliver Lodge in the ether

It is first most important to know that Oliver Lodge was wrong. He successfully transmitted radio signals on August 14th, 1894 making him one of the very earliest to do so. But his theory of it's function was pure bunk. He wrote a book "The Ether of Space" which proposed the ether occupied all space that was otherwise apparently empty. He placed it on the mantle with the Alchemists understanding of matter: earth, water, air... ether. In all fairness... Newton believed in ether too.

Lodge performed his demonstration one year after Tesla transmitted a radio wave, but still before Marconi managed the feat. It makes him an early pioneer, and one that's often overlooked. He was the physicist that used the term "coherer" to describe the early radio detecting device. Branly called it a "radio-conductor"a term that didn't catch on.

Lodge was a believer in the aether (ether). He believed that radio waves occupied a somewhat fantastical medium called ether which only radio waves could pass through. He demonstrated this at a meeting of the British Association for the Advancement of Science at Oxford University. he was a professor of physics and mathematics at University College in Liverpool and one of the few people alive at that time who could assemble such a device.

Lodge used a Coherer based on Edouard Branly's coherer design. But he made one small improvement. That early coherer was a glass tube of metal filings. When a current was applied they clung together lowering the resistance. Lodge created what he called a "trembler" which shook them apart to return the resistance to it's initial value, restoring sensitivity. This "trembler" was literally a tiny mallet. I don't mean to deprecate the improvement; that separate concept was important. Later revisions led to what was called a decoherer, a "trembler" powered by the cohering current. Tesla's improvement to the trembler simply rotated.

Lodge was a little crazy. He was a firm believer in life after death, and was known to consult psychic mediums who helped him consult with death friends and relatives. This is probably where that ether crap originates from. Nonetheless in 1898, Lodge applied for a patent [ 609,154] for an adjustable induction coil that made it possible to tune the transmitter and receiver. Within the decade the coherer was sidelined in favor of crystal tuners, but tuning, that improvement was fundamental. As late as 1943 American courts were affirming Lodge's patent over Marconi's tuned circuits.Radio wasn't everything. He invented the spark plug, the loud speaker and was knighted in 1902. He retired in 1919 from teaching and ether in general to the family trade; a clay merchant.